Rheostat.



No. 7|5,a27. l Patented nec. la, 1902.

F. MAcKmTosH.

RHEUSTAT.

(Application Bled May 22, 1901.)

(No Model.)

Wifnesses I rn/enor W? FecleljickMackinfosh UNITED STATES PATENT OFFICE.

FREDERICKMACKINTOSH, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

RH EOSTAT.

SPECIFICATION forming part of Letters Patent No. 715,827, dated December 16, 1902 Application filed May 22, 1901. Serial No. 61,347. (No model.)

TolaZZ whom, it may concern:

Be it known that I, FREDERICK MAOKIN- TOsH, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Rheostats,.

(Case No. 2,2b'9,) of which the following is a specification.

This invention relates to rheostats for electric circuits, the object being to permit freer ventilation than is commonly provided in devices of this character, and thereby prevent excessive heating under large currents and to simplify and cheapen the construction. I promote free ventilation by forming the resistance-conductor of wire, with all parts of itslength freely exposed to the atmosphere and out of contact with the framework, and mount the sectional units of the device on insulating-supports suspended in an open-work frame through which the air may circulate; The insulators may be formed of porcelain in the shape of a hollow plug havinga iiauge which rests in openings in the perforated frame. The framework may be of any desired character, the top and bottom frames, which carry the insulators, being preferably formed of a network of iron wires through all parts of which the air may circulate,

The novelty of the invention will be more fully hereinafter described and will be definitely indicated in the claims.

In the accompanyingdrawings, which illustrate the invention, Figure l is a top plan of arheostatcontainingmyimprovements. Fig. 2 is a side elevation, partly in section.

l represents a metal framework supported on feet 2 2, the several parts of which may be formed of channel-iron,connected together by bolts at the joints, as indicated at 3. The frames which carry the rheostat units are secured to bars 4, upon which are riveted or otherwise secured the endsof iron wires 5 crossing each other at right angles and woven into a network or screen having large meshes in which maybe inserted porcelain plugs 6, provided with a flange at the top, as indicated at 6, Fig. 2, and a hole to accommodate the end of the resistance-wire. The resistance units may be formed of an open helix or other form of German silver or iron wire, as indicated at 7, Fig. 2, the top ends and the bottom ends of adjacent units being bent over and permanently connected by wrapping with wire and soldering, as indicated in Fig. l. The several units composing the rheostat are thus connected in series from one end 8 to the other, 8, and taps, as 8b, as many as may be desired, are led off from intermediate points to permit graduation of the resistance in a circuit. The porcelain plugs are held in place by the tension of the several helical units which compose the rheostat. This plan of construction affords a rheostat light in weight, the metal parts having large radiating-surface and a maximum facility of air circulation, thus permitting a maximum carrying capacity for a given sizeof the resistance medium.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

l. A rheostat comprising a plurality of resistance units supported at opposite ends between open-work frames.

2. A rheostat comprising a plurality of resistance units supported between two openwork frames and carried by insulating-supports mounted in said frames.

3. A rheostat comprising a plurality of resistance unitshaving allparts of their length exposed to the air, each unit being supported between two wire screens and mounted on heat-refractory insulating-plugs carried by said screens.

4:. A rheostat comprising a plurality of helices of resistance-Wire, the opposite ends of each helix being supported in an open frame, the several helices being connected in series relation, and circuit connections from intermediate points of the group of helices.

5. A rheostat comprising a framework and network-supports for the resistance-wire carried thereby, insulators mounted in the meshes and resistance units carried by insulators mount-ed on the two open-work supports.

6. A rheostat Comprising a supporting- In witness whereof have hereunto set my framework provided with opposite network hand this 20th day of May, 1901. sides hollow insulators mounted in the l Y nieshes, and resistance units supported be- FREDERICK MACKINTOSH 5 tween said insulators, the ends of said units Witnesses:

passing through the insulators and secured BENJAMIN B. HULL,

to the ends of adjacent units. MARGARET E. WOOLLEY. 

